1al_orthographic_transform(3) al_orthographic_transform(3)
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6 al_orthographic_transform - Allegro 5 API
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9 #include <allegro5/allegro.h>
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11 void al_orthographic_transform(ALLEGRO_TRANSFORM *trans,
12 float left, float top, float n,
13 float right, float bottom, float f)
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16 Combines the given transformation with an orthographic transformation
17 which maps the screen rectangle to the given left/top and right/bottom
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20 near/far is the z range, coordinates outside of that range will get
21 clipped. Normally -1/1 is fine because all 2D graphics will have a z
22 coordinate of 0. However if you for example do al_draw_rectangle(0, 0,
23 100, 100) and rotate around the x axis ("towards the screen") make sure
24 your z range allows values from -100 to 100 or the rotated rectangle
25 will get clipped.
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27 Also, if you are using a depth buffer the z range decides the depth
28 resolution. For example if you have a 16 bit depth buffer there are
29 only 65536 discrete depth values. So if your near/far is set to
30 -1000000/1000000 most of the z positions would not result in separate
31 depth values which could lead to artifacts.
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34 5.1.3
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37 al_use_projection_transform(3), al_perspective_transform(3)
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41Allegro reference manual al_orthographic_transform(3)